I am thinking to do the environmental flow assessment in a river basin, But i have only last 10 years of streamflow data. Please suggest if i can do some assessment regarding this?
Research in general is very flexible. The idea is to do the best based on what you have, still you have to justify all your choices. Additionally, you would support your claims with evidence from previous research.
For example, if your analysis requires a data span more than 10 years, based on previous studies, then you would acknowledge it as a limitation. Otherwise, you have a supporting evident that what you are doing is relaible.
Given the changing climate, you would mention that you expect deviation/consistency. This should be supported by findings from literature about the future projections in the region.